1. Field of the Invention
The present invention relates to a peer-to-peer (P2P) type communication system including a plurality of node devices mutually communicable through a network.
2. Discussion of Related Art
There is known a technology called “Application Layer Multicast (ALM)” where content data stream is relayed and delivered while a delivery (broadcast) route of content data is managed in an application layer. For example, in a tree-type broadcast system which is disclosed by Patent Document 1, plural node devices participating in the system form a plurality of hierarchy levels with a broadcast station (e.g. broadcast device) ranked as a top and are connected in a tree-like form through a communication means at the same time. Content data broadcasted (streamed) from the broadcast station are sequentially transferred from node devices in an upper hierarchy level to node devices in a lower hierarchy level.
In such a tree-type broadcast system, there exist two methods: a control method that a connection destination introduction server as a center equipment centrally controls an entire tree topology (delivery topology) (hereinafter referred to as “ALM control method based on hybrid type P2P”) and a control method that an individual node device dispersively controls partial tree topology (hereinafter referred to as “ALM control method based on pure type P2P”).
[Patent Document 1] Japanese Unexamined Patent Publication No. 2006-33514